/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/MeshNormalsFunctions.h
Set the triangle-vertex normals for the given TriangleID on the TargetMesh. This will create unique triangle-vertex normals, ie it will create hard edges / split normals in the normal overlay for each edge of the triangle.
static [UDynamicMesh](API\Runtime\GeometryFramework\UDynamicMesh) * SetMeshTriangleNormals ( [UDynamicMesh](API\Runtime\GeometryFramework\UDynamicMesh) * TargetMesh, int TriangleID, [FGeometryScriptTriangle](API\Plugins\GeometryScriptingCore\GeometryScript\FGeometryScriptTriangle) Normals, bool & bIsValidTriangle, bool bDeferChangeNotifications )